This invention relates to a water repellent composition for pourous substrates formed by combining an alkylalkoxysilane with a carrier selected from the group consisting of alcohols, mineral spirits, and glycol ethers, together with an effective amount of a surface depositing water beading agent for producing on the surface of the porous substrate a water beading-water shedding surface coating, and a metal salt catalyst. More particularly, the invention relates to such compositions as well as to methods of producing on a pourous substrate a water beading-water shedding surface coating with the compositions.
Water resistance is an important factor in concrete and masonry construction. This is for the reason that moisture movement in concrete causes or contributes to problems such as expansion, shrinkage, cracking, staining, mildew, lowered resistance to freezing and thawing, chemical attack, corrosion of reinforcing steel, and damage to structures from settling. Because of these problems, various techniques have been used for water repellency including the surface treatment of concrete structures with repellents. Repellents that have been used in the past are oils, waxes, soaps, resins, and silicones, and they have been applied to the masonry surfaces by brush, roller, air spray, or airless spray techniques. One of the most prevalent category of repellent that has been used is silicones, and silicones in organic solvents have been found to be useful for brick, concrete, stucco, or terrazo surfaces. Exemplary of such prior art techniques for rendering concrete water repellent by means of silicones can be found in U.S. Pat. No. 3,772,065, issued Nov. 13, 1973, and U.S. Pat. No. 4,342, 796, issued Aug. 3, 1982. A purportedly improved technique is disclosed in U.S. Pat. No. 3,879,206, issued Apr. 22, 1975, where certain additives are included with the silicones. However in contrast to the latter patent, the technique of the present invention differs in providing for a mixture of particular alkylalkoxysilanes; a combination of carrier materials; beading agents of particular compositions; an overall repellent composition of specific formulation; and a surface beading oil effect function and result. While the techniques of the prior art can penetrate and thereby render surfaces water resistant, they have not to any substantial degree done anything to block the pores on the surface of the structures since as previously noted, the repellent penetrates into the structure and then cures to a resinous matrix therewithin. The result is that such products do not bead water on the masonry surface in the fashion of the oils, and while the oils do not have the longevity or the penetrating power of silane, for example, the oils are visually striking in their ability to bead and shed surface water. Such disadvantages of the prior art are overcome with the present invention wherein there is provided compositions and methods in which the advantages of both the silane and the oil types or repellents are combined in order to impart to silanes the visual property and affect of water being repelled.